Hi, KyaniteKirin,
There are other more technically inclined folks who might have suggestions for you, but in your shoes I would try two things: 1) Try meeting up with your cousin in the instance if they are able to play through the mission with you. It sounds like you’re your trying to play The Ghosts and the Darkness, by Eleanor Franklin. You might be able to get in that way. 2) put in a request to a GM to assist you in game.
Last but not least, you might be able to talk to someone in Sanctuary Chat to see if they would be able to assist you with a meet up - type /chat join #sanctuary to access it. (For more info on chat, check this link: How to use chat? ) That channel is a great all-around resource for help with things in game.